Electric circuit



(No Model.)

J. J. CARTY.

ELECTRIC CIRCUIT. No, 399,377. Patented Mar. l2, 1889.

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JOHN J.

STATES, PATENT Orme'.

CARTY, OF 4NEY YORK, N. Y., ASSIGNOR TO THE AMERICAN BELL TELEPHONE COMPANY, OF BOSTON, lllASSACHllSETTS.

ELECTRIC CIRCUIT.

SPECIFICATION forming part of Letters Patent No. 399,377, dated March l2, 1889.

Application led January 23, 1889. Serial No. 297,270. (No model.)

To MZ whom z'v' 71mg/ concern:

Be it known that l, JOHN J. ("ARTY, a citizen of the United States, residing' in New York, in the county and. State of New York,

have invented certain new and useful Improvements in Electric Circuits, of which the tollowii'ig is a specification.

The invention relates to certain improvements in the construction of telegraph or telephone lines. lts primary objects are to provide means for preventing, in so far as is possible, the detrimental eiiects occasioned lrv induction and to decrease the resistance oi' long;` circuits.

It has locen customary to l wist the outgoing' and return wires ot Ametallic circuits about each other tor the purpose, as shown in YLetters Pat-ent issued to David l'rooks, lfehruary 22, 1881, No. 238,195, of placing' each wire in the same relation to external single-wire circuits, so that wl'latever ellfeet may he developed inductively hv such circuits upon the outgoing' cl'nuluetor will he twat-tlv neutralized hy an equal hut oppositely-acting elicct upon and i n the return-c4uiductor. ln a patent issued to me August ill, 'l S813. No. illl, there is described a s vstem in which two eonductors are employed in place of a single main line tor operating' apparatus l )y cu rrent's transmitted upon lhoth lines, and in a pending' application, Serial No. 2l\,llil,l have described tertain modiliczitiots ol' such a system. present. invrnition is designed to he employed in connection with such` an arrangement ol' circuits, and in general terms it provides that' the two wires ol a sine'le pair twisted, transposed, or crossed with one another symmetrically, so as to be neutral to a similar metallic circuit adjacent thereto, mayY in turn constitute one side ot an independent circuit ot' which the. other side is Vformed ol' the two wires oi a second pair, and that when so arranged the two pairs ot' wires forming the said independent circuit shall also lhe crossed or causedV to change places with one another in a manner analogous to the crossings of the two wires oi each oiA the said two pairs, i'or the purpose of maintaining,l neutralit y between strung' upon poles, or, the wires ot each pair being twisted together, the circuits may in a manner well understood be formed into a cable. vThe proper crossings of the two meinhers of the compound circuit being` made at convenient distances apart, the initial trans positions between the two wires ot each of the iirst pairs are in cables unnecessary, the twisting' ot the said two wires together serv ing' in lieu thereof.

In the accompanying' drawings, Figure l is a diagram illustrating' the construction ot' a compound circuit constructed in accordance with this invention. Fig'. 2 shows a similar circuit in which the instruments and their relative positions in the circuit are more clearly indicated, and Fig'. 2S shows a compound metallic circuit in inductive proximity to an external circuit illustrative of the inode in which reciprocal neutrality is eftectuated hetween such circuits lilv my in vention.

Referring' to Figs. l and 2, .ft and 13 represent main metallic circuits of a telephonie system, L L being' respectively the two wires ot one circuit, while L" and LW represent' the two wires ot another. These ma)v lire joined up, as shown, to form a third metallic circuit', extending' hetwecn terminal stationsll and .l, ol which A forms one conductor and B the other. Each oltheoriginalcircuits A and l is provided with electricalV transmittine; and receiving' instrumentsl, f, 1', and fm', the said instruments heilig respectively included. in their several circuits inthe usual way, t working' rccipimally with t in circuit, A. and with '/f iu circuit l.

The several instrumentis` t connected with the initial circuits are shown in 'Fig'. 2 as mac'- neto-t'elei'ihones. each provided with. two separate coils, and these coils are so connected with respect to one another that the currents the said independent compound circuit and i an adjacentexternal circuit.

rlhese circuits traversing the reeeiviiig-instrument coils ol' the circuits A and 13, in their individual sense.

' 1'e-enili`orce each other in the coils olt their rcspcctive instruments. It \\'ill,h wcver, he ol)- served that the conducting-links n, which at the stations ll and J unite the two circuits A and B to form the third and compound circuit, connect with the said circuits A and B at a pointbetween the two coils ot the several instruments t and IH; or, it there be but one continuous coil to the said instruments, the ends of the said link n would conneet with points p at the center thereof. Considering now the circuit C as a whole, it will be seen' that it also is provided with commucating-instruments t5 t, shown also as magneto-telephones, which may be and preferably are included in the connecting-.links n which unite the two initial circuits to form the third.

The currents from the instrument serve to operate the instrument t, and, conversely, t5 is responsive to im; but the currents from these instruments do not operate the instruments t', t, t, or 17', because the two lines of the circuit A constitute one side, while the two lines ol ll constitute the other side, of the circuit traversed by the currents develolgied by t or 1', and thus the instruments if or t, when operated, develop at anyven time eurrents in the same direction in the line L and L, but in opposite direction thereto, in the lines L and L. lVhile, therefore, these currents combine to operate their respective receivers t or t", as the ease may be, they are adapted to exercise equal and opposin effects in the coils ot' the instruments t t and t tm interposed directly in the respective circuits A and B, these being necessarily, therefore, irresponsive.

To sum up: The instruments t and t are reciprocally responsive to one another, their currents circulating in the two wires L and L of themetallic circuit A only. So, also, instruments t and are reciprocally responsive to one another and in the same way serve their eircuitrl exclusively, their currents traversing in one direction the line L and in the other the line L, and in like manner the instruments and t reeiprocally operate each other exclusively in the compound circuit (l, their currents traversing the two wires of the elemental circuit A in one direction and returning by way of the two wires of the other elemental circuit, B.

Referring now to Fig. 3, which shows thc essence of my invention, the former figures being largely of an explanatory character, a description will be given of the construction of the elemental and composite metallic eircuits with reference to any external conductor, whereby inductive neutrality is maintained between the said metallic circuits and the said external conductor and between the said several metallic circuits themselves. In the figure .111/ represent an external circuit, adjacent, however, and within inductive proximity to the compound circuit (i and its elements A and B. In a manner well understood, the two wires of the elemental circuits A and 'il are each crossed with one another or exchange places at suitable points, so as to achieve neutrality between each of. the said metallic circuits and. the foreign circuit my, the wires L and L ot' A being crossed at points l, 2, 3, and l, and those et circuit B being crossed at points 5, 7, 9, and ll. It is,

however, also known that ifA the circuits A and B be crossed in the same manner as each other, while it is true that both are rendered neutral with respect to the external circuit my, their indu etive iniiuenee upon each other remains uiuliminished. tare therefore must be taken to prevent this. To this end, in addition tfo crossing the two wires ot each of the two circuits A and l5 at like points and at regular distances, the wires of one ot the circuits-in this instance ll-are also crossed with one another or exchange places at intermediate points, and thus interference between the two elemental metallic circuits A and B is prevented. The same method of transposition is employed when the four wires are used in forming the third circuit C, using the con ductors L and L asone side and L and L as the other, as vit will be seen that the pairs of wires are so crossed at a, h, and c and their positions so changed relative to each other that any external conductor or circuit, as my, is under the influence of equal lengths of both sides of the circuit, and reciprocally exerts its influence equally on both sides A B of the circuit, setting up at the same time induced currents of like direction in both sides, which oppose one another and have a ml effect on the instruments in the said circuit.

The cross-connecting can be done either at intermediate stations or on the poles, or in the case of subterranean lines at suitable testboxes.

It is not. always necessary that the crossconnecting should be continued throughout the entire lengths of the line, but only in those positions where the induction is most troublesome. Aga-iu, the lengths of the sections and the frequency of the cross-connecting need not be the same in all of the lines, but may be changed to suit the varying conditions of different systems. 'The system is of course not limited to four lines, but may be extended as desired. The invention is particularly applicable to cables in which multiple arrangements otl conductors are to be made, and where, owing to the proximity of the conductors to each other, the effects ot' induction tend to be emphasized.

The conductors may be formed into a cable and caused to assume the positions toward each other which have been described by dividing the cable into sections and cross-com necting; but the wires may be twisted or grouped together in any weltkn own manner, provided that the outgoing' and return meinbers of all of the circuits, whether the said members be elemental. or compound, as herein described, shall be so arranged that any ot' the circuits composed of them in the said group may be brought under the in liuence of equal lengths of the two sides of any other given circuit, as set forth. ln this invention the fact that multiple telephone-"circuits, or metallic circuits in which each side thereof is composed et the outgoing' and return wires of IOO one or more complete metallic circuits, tor the purpose of multiplying the number' of messages which can be transmitted simultaneously over a given number of wires, or for the purpose of reducing circuit-resistance, require equally with simple metallic circuits to be made neutral with respect to external circuits, is fully recognized, and a inode is devised for aeeomplishing the said neutralization, for it is evident that by the construction shown and described four wires are arranged so as to constitute three independent circuits, in which A is formed of the two wires L and L, B of the two wires L" and LW', and C of the circuits A and B, each treated as a single conductor, and that not only are A and B both made neutral to an external conductor, my, by proper cross-connections of their respect-ive outgoing and return wires, and made neutral to one another by intermediate crossings of the two wires ot' one of them, but the compound circuit C is also made neutral to the said external circuit by cross-connecting the two pairs of wires A and B formingits sides.

I claim as my inventionl. In a telephone system an electrical circuit eonsisting of two pairs of main lines, the lines composing each pair being transposed at intervals, and said pairs being transposed at intervals.

2. An electrical circuit or system of circuit-s consisting of two pairs of main lines, the outgoing and return conductors of each pair being transposed at intervals, and said pairs being transposed at intervals, in combination with electrical instruments for producing eurrents in each pair and an electrica-l instrument for producing currents in all of the lines, substantially as described. q,

In testimony whereof l have hereunto subscribed my name this 22d day of January, A. D. 1889.

JOHN J. CARTY.

Witnesses:

DANL. W. EDcEoonB, CAROLINE E. DAVIDSON. 

